Cone beam computed tomography (CBCT) is an X-ray imaging modality capable of acquiring three-dimensional information from the human anatomy with a lower radiation dose to the patient as compared to conventional medical computed tomography (CT) systems. Cone beam CT systems capture volumetric data sets by using a high frame rate digital radiography (DR) detector and an x-ray source. The detector and source are typically affixed to a gantry that rotates about the subject to be imaged, with the source directing, from various points along its orbit around the subject, a divergent cone beam of x-rays toward the subject. The CBCT system captures projections at rotation locations, for example, one 2-D projection image at every degree of rotation. The projections are then reconstructed into a 3D volume image using various techniques. Known methods for reconstructing the 3-D volume image include filtered back projection approaches.
One area for CBCT use is endodontics. In conventional practice, detection of a problem responsive to endodontic treatment begins with the patient's report of pain. The practitioner works with the patient to isolate the suspect tooth and may obtain one or more two-dimensional (2-D) periapical radiographs to help identify any abnormalities of the root structure and surrounding bone structure. In some situations, visual inspection of the 2-D image can help to identify the problem. However, detection of some types of conditions remains a challenge with conventional 2-D images. For example, some types of vertical root fracture (VRF) can be difficult to detect in the periapical image. Vertical root fracture is a type of tooth fracture that affects the root, causing pain due to infection and inflammation and often necessitating tooth extraction.
CBCT imaging and its capability for displaying low contrast tissue regions makes CBCT a technology for assessment of VRF and other endodontic conditions. This includes use of CBCT imaging to support root canal therapy, as shown in the sequence of FIG. 1. In this type of treatment, an infected tooth 20 has an abscess 22 to be treated. An opening 24 is made in tooth 20 and a tool 28 is used to access and remove infected material. A plugger 30 then fills root portions of tooth 20 with gutta percha or other suitable material. The tooth 20 can be repaired with a filling 34 or a crown 36 that is fitted onto a post 38 inserted by the practitioner.
While CBCT imaging can be used to improve detection of VRF and other conditions requiring endodontic treatment or other types of treatment, however, difficulties remain. Manipulating the CBCT image can be challenging, particularly for practitioners/technicians who are new to volume imaging technology. Isolating the particular views that most distinctly reveal the problem condition can be difficult or frustrating for the practitioner, burdening the user with a time commitment for training and for using the CBCT system.
Computer-aided diagnostics (CAD) systems have been used, with the goal of analyzing image contents and identifying suspected root fractures or other lesions for display to the operator. Such systems have had some success, but there is room for improvement. Existing systems typically provide minimal interaction with the user, making it difficult to determine the likelihood or severity of a condition. The relative number of false negative and false positive indications provided from these systems makes it difficult for the practitioner to verify the results of the automated analysis. The 3-D perspective view can be limited in function and difficult to operate.
Thus, there is a need for an interactive user/operator/practitioner interface that provides accurate reporting of VRF and/or other problems, provides image manipulation tools that can be quickly learned, and provides an intuitive viewer experience, allowing the user to make effective use of CBCT imaging for endodontic applications.